Object Query Language (OQL) is a
query language standard for
object-oriented databases modeled after
SQL and developed by the
Object Data Management Group The Object Data Management Group (ODMG) was conceived in the summer of 1991 at a breakfast with object database vendors that was organized by Rick Cattell of Sun Microsystems. In 1998, the ODMG changed its name from the Object Database Management Gr ...
(ODMG). Because of its overall complexity the complete OQL standard has not yet been fully implemented in any software. The OQL standard influenced the design of later query languages such as
JDOQL and
EJB QL
EJB QL or EJB-QL is a portable database query language for Enterprise Java Beans. It was used in Java EE applications. Compared to SQL, however, it is less complex but less powerful as well.
History
The language has been inspired, especially EJB3 ...
, though none are considered to be any version of OQL.
General rules
The following rules apply to OQL statements:
* All complete statements must be terminated by a semi-colon.
* A list of entries in OQL is usually separated by commas but not terminated by a comma(,).
* Strings of text are enclosed by matching quotation marks.
Examples
Simple query
The following example illustrates how one might retrieve the
CPU
A central processing unit (CPU), also called a central processor, main processor or just processor, is the electronic circuitry that executes instructions comprising a computer program. The CPU performs basic arithmetic, logic, controlling, and ...
-speed of all PCs with more than 64MB of
RAM from a fictional
PC database:
SELECT pc.cpuspeed
FROM PCs pc
WHERE pc.ram > 64;
Query with grouping and aggregation
The following example illustrates how one might retrieve the average amount of
RAM on a
PC, grouped by manufacturer:
SELECT manufacturer, AVG(SELECT part.pc.ram FROM partition part)
FROM PCs pc
GROUP BY manufacturer: pc.manufacturer;
Note the use of the keyword
partition, as opposed to aggregation in traditional SQL.
See also
*
Object Data Management Group The Object Data Management Group (ODMG) was conceived in the summer of 1991 at a breakfast with object database vendors that was organized by Rick Cattell of Sun Microsystems. In 1998, the ODMG changed its name from the Object Database Management Gr ...
(ODMG)
* Object Definition Language
Query languages
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